1. Field of the Invention
The present invention relates to a gas generator for an air bag which can be suitably used in an inflating-type safety system for motor vehicles, and more particularly, to a multistage type gas generator for an air bag provided with a plurality of combustion chambers and which is preferable for mass production and a stabilized operation performance.
2. Description of the Related Art
An air bag apparatus which is mounted on various kinds of vehicles including automobiles, aims to hold an occupant of the vehicle by means of an air bag (a bag body) that rapidly inflates by a gas when the vehicle collides at a high speed in order to prevent the occupant from crashing into a hard portion inside a vehicle compartment such as a steering wheel and a windscreen due to an inertia to prevent the occupant and from being injured. This kind of air bag apparatus generally comprises a sensor, a control unit, a pad module, and the like, and the pad module comprises a module case, an air bag, a gas generator, and the like, and it is mounted, for example, on a steering wheel.
The gas generator is constituted such that, when igniting means is actuated by an impact, gas generating means is burnt to generate a high temperature, high-pressure gas, and the generated gas is ejected into the air bag (a bag body) such that the air bag is inflated to form a cushion between the steering wheel and the occupant to absorb the impact.
Various kinds of gas generators have been developed, such as ones having different shapes to be mounted on different part of the vehicle, or ones having different numbers of combustion chambers that accommodate gas generating means to control output aspects of the generated gas for inflating the air bag.
Among them, a gas generator provided with a plurality of combustion chambers for accommodating a gas generating agent has been disclosed in JP-A 09-183359, JP-A 11-217055, or the like.
However, in these conventional gas generators, there are rooms for improvement in manufacturing easiness or the like.